Canvas

A composable that hands you a DrawScope over a blank Swing surface so you can draw whatever you like.

Repaint is snapshot-observed. Any snapshot state you read directly inside onDraw is tracked; when such state changes the surface repaints and re-invokes onDraw automatically. Read your state where you use it, at paint time:

var radius by remember { mutableFloatStateOf(10f) }
Canvas(modifier = SwingModifier.preferredSize(Dimension(200, 200))) {
    drawCircle(Color.RED, radius = radius)
}

The drawing is a draw node appended to modifier, so it runs inside every decoration modifier declares. The surface is non-opaque and paints no background of its own: only what onDraw renders appears. Size it with the preferred-size modifier (see org.jetbrains.compose.swing.modifier.layout.preferredSize); without one it asks only for the paint outsets its decoration needs.

Parameters

See also